Cathode ray tube control circuits



April 1'1, 1939. Y R. URTEL ET AL 2,153,655

CATHODE RAY TUBE CONTROL CIRCUITS Filed July l5, '1956 DEFLEGTING Con.

DFLEcrma con.

ATTORN EY Patented Apr. 11, 1939 UNIED STATES TENT OFFECE CATHODE RAYTUBE CONTROL CIRCUITS Application July 15, 1936, Serial No. 90,706 InGermany July 8, 1935 1 Claim.

The invention relates broadly to control circuits for cathode ray tubesand more specifically to a circuit arrangement whereby the production ofthe cathode ray beam in the tube may be blocked or diminished when thedeflecting means for the tube are being energized in such fashion as toreturn the beam to some initial or base point from a position towhich ithas been previously denected.

This is particularly important Where the cathode ray tube is employed asa television receiving element and where the beam has swept across oneline of the picture and must be returned to the beginning of the linewithout alecting the picture detail. If the beam is allowed to sweepback across the fluorescing screen with any intensity, the iiuorescentscreen is brightened for thatline and hence picture detail is affectedas well as a flicker effect being produc-ed.

According to the invention, a portion of the energy used to return thebeam to the initial point, or an energy operating synchronouslytherewith, is joined in seiies to a rectiiier, in this instance, a dryrectifier, which is triggered by a biasing arrangement, as for instance,a steady voltage, so that the rectified energy produces a voltage inexcess of the triggering voltage and the excess is used as a blockingvoltage in the control circuit for the cathode ray beam.

The invention will best be understood by reference to the accompanyingdrawing in which:

Figure 1 shows a schematic embodiment of our invention.

Figure 2 shows a modified arrangement according to Figure 1, and

Figure `3 shows still another embodiment of our invention.

Referring to Fig. l, I0 represents a coil connected in the deflectionenergy circuit of the cathode ray tube, and may be the magneticdeflection coil of the tube itself. Inductively coupled thereto is acoil I I across which is connected a loading resistor I2. Joined inseries with this parallel arrangement is a rectifier I3, a resistance I5and a biasing voltage I4. The direction of the induced Voltage in the-coil II when the beam is being returned to its initial position isindicated by the positive and negative signs thereon. Joined in serieswith the resistor I5 is the secondary of a transformer I9 whose primaryis energized by the picture signals with which th-e cathode ray beam ismodulated, the control electrode of the tube I6, said control electrodebeing indicated as 20, a biasing voltage I8 and the cathode of the tubeIl.

(Cl. Z50-27) The circuit arrangement shown in Fig. 1 functions in such afashion that during the energizing of the deiiecting members of the tubeI6 in such manner as to return the beam to its initial position, thereappears in the coil II a voltage, the 5 direction of said voltage beingindicated by the positive and negative signs on the diagram. Thedirection of this voltage is such as to oppose that of the biasingbattery I4 and hence, if it is greater than the Value of the voltage I4, it will cause a l0 current to flow through the series circuitcomprising the coil II, rectifier I3 and resistor I5. The resistor I5being connected in series with the cathode I'I of the tube I6, thesecondary of transformer I9 and a control electrode 20 of the tube, 16the control electrode 20 will be biased with respect to the cathode ofthe tube by an amount equal to the voltage drop across resistor I5, andhence if the value of this voltage be suiiicient, the cathode ray beamwould be blocked. 20

When the dellecting members of the tube have returned to a state whereinthe cathode ray beam, if produced, would impinge at the initial point,the dir-ection of the deecting voltage changes so as to sweep the beamback again linearly across 25 the screen. During this time the voltageinduced in coil I I would be in a'direction opposite to that indicatedby the signs, hence coil II would tend to oscillate at its naturalfrequency due to the collapse of current through the rectifier. The re-30 sistor I2 acts as a damping member to suppress the production of' avoltage o-n the positive half of the oscillation which might exceed theValue of the biasing battery I4 and hence cause a rectified currentwhose Voltage drop across the re- 35 sistor I 5 would tend to eithersubstantially reduce or entirely block the production of the cathode raybeam.

The arrangement shown in Fig. 2, substitutes an auto-transformerarrangement for the two 40 coils I0 and Il of Fig. 1. In this case thepotentials opposite to that in the arrangement shown in Fig. 1 andtherefore the rectifier connections and biasing member are changedaccordingly, that is to say reversed. The voltage drop through 45resistor I5 is opposite to that in Fig. 2 and therefore the controlelectrode and the cathode are suitably connected thereto or, in otherwords, the connections to the resistor I5 are, in Fig. 2, reversed inposition from those shown in Fig. 1. 50 The operation of the circuit isthe same.

Referring to Fig. 3, the resistor I5 has been supplanted in position bythe rectier I3 and it is the potential across the rectifier and notacross the resistor which serves the control elements of 55 the tube. Inthis case, in order to limit the current passing through the rectifier,it is advisable to provide a resistor element 2| connected as shown inthe diagram. The direction of the potential source I4 and the rectier inFig. 3 correspond to those in Fig. 1. However, it is obvious that thecircuit may be modified in the manner suggested in Fig. 2.

What We claim is:

An apparatus for controlling the production of a cathode ray beam, acathode ray tube having an electromagnetic beam deection coil fordeflecting the cathode ray beam comprising a deflection voltage circuit,a deection coil energized from said circuit, electrical means coupled tothe coil connected to the deection Voltage circuit so that the coupledcoil forms a transformer secondary and derives energy from thedeflecting coil, a first series electrical circuit comprising saidcoupled electrical means, a rectifier and a resistor, a second seriescircuit comprising a control electrode of the cathode ray tube, theaforementioned resistor, the cathode of the cathode ray tube and 10 asource of modulating potential.

RUDOLF URTEL. ROBERT ANDRIEU.

